Resistors are used in the analog circuit of semiconductor integrated circuit. Resistors used in a semiconductor integrated circuit are of various types, such as a diffusion resistor provided on the surface of a semiconductor substrate and a polycrystalline silicon resistor provided above the surface of a semiconductor substrate, but a variation in the resistance value of the resistance element occurs unavoidably in any case. When an analog integrated circuit is designed, therefore, it is necessary to presume beforehand that a certain degree of variation in resistance value will exist. One method of solving the problem of resistance-value variation is to integrate a circuit, which is for detecting the variation in resistance value, with the integrated circuit. By using this circuit, each chip itself evaluates the resistance variation of the chip and supplies the result to other circuit elements, whereby a suitable correction is applied for each individual element circuit. As a result, a decline or fluctuation in performance ascribable to a variation in resistance value can be suppressed, or it is possible to reduce excess current consumption for achieving operation margin even under worst-case conditions.
FIG. 1 of Patent Document 1 illustrates a circuit provided with a resistor network R(1) to R(N) that is dependent upon temperature variations and a reference resistor 105 that is independent of the temperature variations, wherein the resistance value of the resistor network is modified so that this resistance value will be maintained the same as that of the resistance value of the reference resistor. More specifically, resistors R(1) to R(N) that depend upon temperature variations are serially connected and N-number of taps are extracted from this series connection. By using a comparator 135 to find the position of a tap where the terminal voltage of the resistor 105 and potential are in balance, the amount of resistance variation can be determined.
FIG. 3 of Patent Document 2 illustrates a resistance error detection circuit in which current sources (11, 12) are formed in an IC for supplying identical currents to a first resistance element (RB) formed inside the IC and to a reference resistor (RS) provided outside the IC, and which is provided with a differential circuit 13 for outputting, as an analog voltage, the difference between the voltages of the first resistance element (RB) and reference resistor (RS) ascribable to the currents that flow through them.
[Patent Document 1] Japanese Patent Kokai Publication No. JP-A-08-256034, which corresponds to U.S. Pat. No. 5,717,323A.
[Patent Document 2] Japanese Patent Publication No. JP-2732323B